Method and system for condensing water vapour from a carbon dioxide rich flue gas

Abstract

A gas cleaning system is operative for removing water vapour from a carbon dioxide rich flue gas generated in a boiler combusting a fuel in the presence of a gas containing oxygen gas. The gas cleaning system comprises a flue gas condenser ( 12 ) being operative for condensing water from at least a portion of the carbon dioxide rich flue gas generated in the boiler by bringing the carbon dioxide rich flue gas into contact with a circulating cooling liquid, thereby generating a cleaned carbon dioxide rich flue gas having a lower concentration of water vapour than the carbon dioxide rich flue gas leaving the boiler. The gas cleaning system comprises a heat pump ( 100 ) being operative for absorbing heat at a first temperature from the cooling liquid, and for desorbing heat at a second temperature, being higher than the first temperature, to a heat sink ( 124 ).

1 . A method of removing water vapour from a carbon dioxide rich flue gas generated in a boiler combusting a fuel in the presence of a gas containing oxygen gas, the method comprising:
 forwarding at least a portion of the carbon dioxide rich flue gas generated in the boiler to a flue gas condenser;   cooling, in said flue gas condenser, the carbon dioxide rich flue gas by bringing the carbon dioxide rich flue gas into contact with a circulating cooling liquid to condense water from the carbon dioxide rich flue gas, thereby generating a cleaned carbon dioxide rich flue gas having a lower concentration of water vapour than the carbon dioxide rich flue gas leaving the boiler, and   utilizing a heat pump for absorbing heat at a first temperature from the cooling liquid, and for desorbing heat at a second temperature, being higher than the first temperature, to a heat sink.   
     
     
         2 . A method according to  claim 1 , wherein a parameter which is related to the water vapour concentration of the cleaned carbon dioxide rich flue gas leaving the flue gas condenser is measured, and is compared to a set point for that parameter. 
     
     
         3 . A method according to  claim 2 , wherein the operation of the heat pump is controlled based on a comparison between a measured value of the parameter which is related to the water vapour concentration of the cleaned carbon dioxide rich flue gas leaving the flue gas condenser and the set point for that parameter. 
     
     
         4 . A method according to  claim 1 , wherein the carbon dioxide rich flue gas is brought into direct contact with the cooling liquid in the flue gas condenser. 
     
     
         5 . A method according to  claim 1 , wherein the carbon dioxide rich flue gas is indirectly cooled in the flue gas condenser by means of a cooling liquid. 
     
     
         6 . A method according to  claim 5 , wherein the cooling liquid cooling the carbon dioxide rich flue gas indirectly in the flue gas condenser is also utilized as a cooling media of said heat pump. 
     
     
         7 . A method according to  claim 1 , wherein the cooling liquid is supplied to the flue gas condenser at a temperature of 0-35° C., preferably at a temperature of 0-20° C. 
     
     
         8 . A gas cleaning system being operative for removing water vapour from a carbon dioxide rich flue gas generated in a boiler combusting a fuel in the presence of a gas containing oxygen gas, the gas cleaning system comprising a flue gas condenser being operative for condensing water from at least a portion of the carbon dioxide rich flue gas generated in the boiler by bringing the carbon dioxide rich flue gas into contact with a circulating cooling liquid, thereby generating a cleaned carbon dioxide rich flue gas having a lower concentration of water vapour than the carbon dioxide rich flue gas leaving the boiler, the gas cleaning system further comprising a heat pump being operative for absorbing heat at a first temperature from the cooling liquid, and for desorbing heat at a second temperature, being higher than the first temperature, to a heat sink. 
     
     
         9 . A gas cleaning system according to  claim 8 , wherein the gas cleaning system further comprises a sensor which is operative for measuring a parameter which is related to the water vapour concentration of the cleaned carbon dioxide rich flue gas leaving the flue gas condenser, and a control device which is operative for controlling, in view of a comparison of a measured value of said parameter and a set point of said parameter, the operation of the heat pump. 
     
     
         10 . A gas cleaning system according to  claim 8 , wherein said heat sink comprises a cooling tower. 
     
     
         11 . A gas cleaning system according to  claim 8 , wherein said heat sink comprises the boiler. 
     
     
         12 . A gas cleaning system according to  claim 8 , wherein a further heat exchanger and a heat sink are provided for cooling the circulating cooling liquid in series with the heat pump. 
     
     
         13 . A gas cleaning system according to  claims 8 , wherein the heat pump is operative for desorbing heat to a first heat sink and to a second heat sink, being separate from said first heat sink. 
     
     
         14 . A gas cleaning system according to  claim 8 , wherein said heat pump comprises at least two heat pump stages arranged in series. 
     
     
         15 . A gas cleaning system according to  claim 8 , wherein said heat pump is a type of heat pump which is selected from the group of heat pumps comprising ammonia-water absorption heat pumps and carbon dioxide heat pumps. 
     
     
         16 . A gas cleaning system according to  claim 8 , wherein the flue gas condenser is an indirect cooling condenser, the flue gas condenser being operative for functioning as a heat pump evaporator in which a cooling media being circulated in the heat pump is made to evaporate.